U.S. patent application number 10/953072 was filed with the patent office on 2005-07-14 for vehicles and control systems thereof with adjustable steering axes.
Invention is credited to Fenelli, Nicholas.
Application Number | 20050154504 10/953072 |
Document ID | / |
Family ID | 36119602 |
Filed Date | 2005-07-14 |
United States Patent
Application |
20050154504 |
Kind Code |
A1 |
Fenelli, Nicholas |
July 14, 2005 |
Vehicles and control systems thereof with adjustable steering
axes
Abstract
Systems and methods for variably locating the steering axis of
vehicles for achieving improved maneuverability thereof. More
particularly, in some embodiments, systems and methods for
automatically locating the steering axis (the steer center) of
wheeled vehicles according to predetermined and/or detected input
variables. In still further embodiments, systems and methods for
manually locating the steering axis of a wheeled vehicle. In yet
further preferred embodiments, such methods or systems are employed
in vehicles utilizing omni-directional wheel systems, skid steer
wheel systems, conventional wheels, or combinations thereof.
Inventors: |
Fenelli, Nicholas; (Trenton,
NJ) |
Correspondence
Address: |
HALL, MYERS, VANDE SANDE & PEQUIGNOT, LLP
10220 RIVER ROAD, SUITE 200
POTOMAC
MD
20854
US
|
Family ID: |
36119602 |
Appl. No.: |
10/953072 |
Filed: |
September 30, 2004 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
|
|
60506723 |
Sep 30, 2003 |
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Current U.S.
Class: |
701/1 |
Current CPC
Class: |
B62D 15/00 20130101 |
Class at
Publication: |
701/001 |
International
Class: |
G06F 017/00 |
Claims
I claim:
1. A method of controlling the directional motion of a vehicle in
response to at least one selected or detected variable, said method
comprising: variably locating a steer center, corresponding to a
steer axis, of a vehicle in response to said at least one selected
or detected variable.
2. A method according to claim 1 wherein said vehicle is a wheeled
vehicle employing independently driven wheels.
3. A method according to claim 1 wherein said vehicle is a wheeled
vehicle employing independently driven wheels selected from the
group consisting of: omni-directional-type wheels and skid steer
type wheel systems.
4. A method according to claim 3, wherein said vehicle includes a
plurality of wheels, said wheels being located in a pattern, said
pattern having a geometric center, said method further comprising
locating said steer center of said vehicle at a location other than
said geometric center of said wheel pattern of said vehicle.
5. A method according to claim 4 wherein said vehicle travels in a
plane of motion and wherein said steer center of vehicle is
selectively locatable anywhere in said plane of motion of said
vehicle.
6. A method according to claim 5 further comprising actively moving
said steer center of said vehicle, as desired, and performing said
movement of said steer center in response to detection of one or
more variables selected from the group consisting of: rotational
speed, translational speed, preprogrammed definition, or other
external input variables.
7. A method according to claim 4 further comprising: setting a
rotational speed limit of said vehicle based on determining or
detecting a translational speed thereof, a preprogrammed
definition, or other external input variable.
8. A method according to claim 6 wherein said plane of motion is
defined by an area not limited to an area among or between said
vehicle wheels.
9. A method according to claim 5 further comprising methods steps
to maneuver said vehicle rotationally about an object, said method
steps comprising: selecting an object at a location other than said
vehicle or a component thereof; designating said object as said
steer center of said vehicle; and maneuvering said vehicle about
said object by rotating said vehicle about said steer center of
said vehicle.
10. A method according to claim 9 further comprising automatically
rotating said vehicle about said steer center, without operator
intervention, after actuation of a control mechanism of said
vehicle.
11. A method according to claim 10 further comprising the method
steps of: adding a non-rotational component to a movement of said
vehicle as said vehicle rotates about said steer center
thereof.
12. A method according to claim 11 wherein said non-rotational
component is added by operator intervention.
13. A method according to claim 5 further comprising method steps
to maneuver said vehicle rotationally about an operator thereof,
said method steps comprising: determining a location of said
vehicle operator; designating an area proximal said location of
said vehicle operator as said steer center of said vehicle; and
rotating said vehicle about said operator.
14. A method according to claim 13 further including the method
steps of: locating a sensor on said vehicle operator; sensing a
location of said vehicle operator according to a detected position
of said sensor; designating an area proximal said location of said
detected position of said sensor as said steer center of said
vehicle; and rotating said vehicle about said operator.
15. A method according to claim 12 further comprising limiting a
translational speed of said vehicle as a function of rotational
speed, a second translational speed, a preprogrammed definition, or
other external input.
16. A method according to claim 15 further comprising a method of
dynamically scaling vehicle control comprising: actively resealing
input signals as a function of dependant relationships thereof, in
order to maximize input device resolution.
17. A method according to claim 16 further comprising: detecting
vehicle forward speed as one of said input signals; and moving said
steer center of said vehicle in a direction toward said direction
of forward motion in an amount proportional to a magnitude of said
forward speed.
18. A method according to claim 17 wherein said movement of said
steer center in said forward motion direction is automatically
performed by said vehicle.
19. A method according to claim 17 wherein said movement of said
steer center in said forward motion direction is manually performed
by an operator of said vehicle.
20. A method according to claim 9 wherein vehicle rotation about
said steer center is accomplished by an operator providing a single
input to a control mechanism of said vehicle.
21. A system for controlling the directional motion of a vehicle in
response to at least one selected or detected variable, said system
comprising: a control mechanism embodying a set of control
instructions, said control instructions being formulated to perform
the functions of: variably locating a steer center, corresponding
to a steer axis, of a vehicle in response to said at least one
selected or detected variable.
22. A system according to claim 1 wherein said vehicle is a wheeled
vehicle employing independently driven wheels.
23. A system according to claim 1 wherein said vehicle is a wheeled
vehicle employing independently driven wheels selected from the
group consisting of: omni-directional-type wheels and skid steer
type wheel systems.
24. A system according to claim 3, wherein said vehicle includes a
plurality of wheels, said wheels being located in a pattern, said
pattern having a geometric center, and wherein said location of
said steer center of said vehicle is at a location other than said
geometric center of said wheel pattern of said vehicle.
25. A system according to claim 24 wherein said vehicle travels in
a plane of motion and wherein said steer center of vehicle is
selectively locatable anywhere in said plane of motion of said
vehicle.
26. A system according to claim 25 wherein said control mechanism
is capable of actively moving said steer center of said vehicle, as
desired, and performing said movement of said steer center in
response to detection of one or more variables selected from the
group consisting of: rotational speed, translational speed,
preprogrammed definition, or other external input variables.
27. A system according to claim 24 further wherein said control
mechanism is capable of: setting a rotational speed limit of said
vehicle based on determining or detecting a translational speed
thereof, a preprogrammed definition, or other external input
variable.
28. A system according to claim 26 wherein said plane of motion is
defined by an area not limited to an area among or between said
vehicle wheels.
29. A system according to claim 25 wherein said control mechanism,
embodying said control instructions, is capable of: selecting or
allowing a selection of an object at a location other than said
vehicle or a component thereof; designating said object as said
steer center of said vehicle; and controlling said vehicle thereby
to maneuver said vehicle about said object by rotating said vehicle
about said steer center of said vehicle.
30. A system according to claim 29 wherein said control mechanism
is capable of automatically rotating said vehicle about said steer
center, without operator intervention, after actuation of said
control mechanism of said vehicle.
31. A system according to claim 30 further wherein said control
mechanism is capable of adding a non-rotational component to a
movement of said vehicle as said vehicle rotates about said steer
center thereof.
32. A method according to claim 31 wherein said non-rotational
component is added by manual operation of an operator of said
vehicle.
33. A system according to claim 35 wherein said control mechanism
is capable of: determining a location of said vehicle's operator;
designating an area proximal said location of said vehicle's
operator as said steer center of said vehicle; and causing said
vehicle to rotate about said operator about said steer center.
34. A system according to claim 33 further including: a sensor
located on an operator of said vehicle; said control mechanism
being capable of detecting a location of said sensor and thereby
determining a location of said vehicle operator according to said
detected position of said sensor; and said control mechanism being
capable of assigning an area proximal said location of said
detected position of said sensor as said steer center of said
vehicle and thereafter causing said vehicle to rotate about said
operator about said steer center.
35. A system according to claim 32 further wherein said control
mechanism is further capable of actively limiting a translational
speed of said vehicle as a function of rotational speed, a second
translational speed, a preprogrammed definition, or other external
input.
36. A system according to claim 35 wherein said control
instructions include instructions for conducting dynamic scaling of
vehicle control, said dynamic scaling including actively resealing
input signals as a function of dependant relationships thereof, in
order to maximize input device resolution.
37. A system according to claim 36 further including a speed
detector for detecting a forward speed of said vehicle as one of
said input signals; and wherein said control mechanism, upon
receiving information related to said forward speed from said speed
detector, is capable of moving said steer center of said vehicle in
a direction toward said direction of forward motion in an amount
proportional to a magnitude of said forward speed.
38. A system according to claim 37 wherein said control mechanism
is capable of moving said steer center in said forward motion
direction automatically without operator intervention.
39. A system according to claim 37 further including an input
device communicably connected to said control mechanism, said input
device being manually operable by a vehicle operator to move said
steer center in said forward motion direction.
40. A system according to claim 39 wherein said control mechanism
is capable of causing said vehicle rotation about said steer center
upon receipt of a single input signal actuated by a vehicle
operator.
41. A method according to claim 4 wherein said steer center is
located at a location other than the geometric center such that
said vehicle is rotatable about said steer center to facilitate
maneuverability of said vehicle about obstacles.
42. A method according to claim 4 wherein said steer center is
located at a location other than the geometric center such that
said vehicle is steerable about said steer center to facilitate
increased dynamic stability of said vehicle.
43. A system according to claim 24 wherein said steer center is
located at a location other than the geometric center such that
said vehicle is rotatable about said steer center to facilitate
maneuverability of said vehicle about obstacles.
44. A system according to claim 4 wherein said steer center is
located at a location other than said geometric center such that
said vehicle is steerable about said steer center to facilitate
increased dynamic stability of said vehicle.
45. A method according to claim 16 wherein said step of actively
resealing input signals substantially eliminates input dead zones
in manually operable input controls mechanism.
46. A system according to claim 36 wherein said instructions for
conducting active resealing of input signals, when performed,
substantially eliminate input dead zones in a manually operable
input controls mechanism.
47. A system according to claim 46 wherein said manually operable
input control mechanism is a joystick.
48. A method according to claim 1 further including the method step
of automatically determining a center of gravity of said vehicle as
a function of vehicle load position and weight, and automatically
locating said steer center at said center of gravity.
49. A system according to claim 21 further wherein said control
mechanism is capable of automatically determining a center of
gravity of said vehicle as a function of vehicle load position and
weight, and thereafter automatically locating said steer center at
said center of gravity.
Description
RELATED APPLICATION DATA
[0001] This application claims priority of U.S. Provisional Patent
Application No. 60/506,723, filed Sep. 30, 2003, applied for by
Nicholas E. Fenelli, entitled VEHICLE WITH ADJUSTABLE STEERING
AXIS, the entirety of which is hereby incorporated by
reference.
FIELD OF THE INVENTION
[0002] This invention relates to wheeled vehicles having
locationally variable steering axes. More particularly, this
invention relates to wheeled vehicles having steering axes (steer
centers) the locations of which can be automatically defined
according to predetermined or detected criteria, or which may be
operator defined as desired. In preferred embodiments, this
invention relates to omni-directional vehicles, employing
omni-directional wheels, said vehicles having such locationally
variable steering axes.
BACKGROUND OF THE INVENTION
[0003] Heretofore, in known control systems for wheeled vehicles,
it is typical for such control systems to locate the steer center
of the vehicle being controlled (i.e. the steering axis of the
vehicle) at the geometric center of the wheel pattern. In this
regard, the geometric center of the wheel pattern of a four wheeled
vehicle can be found by locating the point of intersection of lines
drawn from the left front wheel to right rear wheel and from the
right front wheel to left rear wheel (the vertical steer axis being
located at such point of intersection).
[0004] In vehicles employing such control systems, therefore, the
control system recognizes or designates the steer center (steer
axis) as being located at the geometric center of the vehicle and
performs all steering functions based on such location thereof.
[0005] It has been discovered, however, that a vehicle which has a
steering axis fixed at its' geometric center is extremely limited
in speed and/or dynamic stability. Furthermore, the ability of the
vehicle operator to walk behind such vehicles when carrying long
loads, for example, is difficult and/or limited. In this regard,
when traveling at significant forward speeds, steering or turning a
vehicle can introduce significant instability to the vehicle
particularly if the vehicle is carrying heavy or unstable
loads.
[0006] Moreover, for vehicles with rotational capabilities, such as
omni-directional or skid steer type vehicles, although it is
possible to maneuver such vehicles in a variety of rotational type
directions, it is often the case that maneuvering about an object,
for example, can require complicated control maneuvers (e.g. with a
joystick) and/or can require significant concentration of the
vehicle operator. Examples of particularly innovative
omni-directional vehicles can be found in U.S. Pat. Nos. 6,340,065;
6,394,203; and 6,547,340, such patents being co-owned herewith, the
disclosures of which are hereby incorporated by reference.
[0007] In response to the above enumerated drawbacks, Applicant has
developed systems and methods by which the steering axis or steer
center of a vehicle can be located or moved, automatically, or
manually as desired, thereby to address and/or solve the above
mentioned problems. In this regard, Applicant has developed methods
and systems by which the steer center of a wheeled vehicle can be
assigned or moved in response to one or more of a plurality of
criteria, such as, for example, vehicle speed and/or vehicle load
(including a vehicle's center of gravity due to load) such as to
maximize or optimize a vehicles dynamic stability.
[0008] Furthermore, Applicant has developed methods and systems by
which increased ease of maneuverability of a vehicle can be
achieved, such as by allowing the assignment of the location of a
steer center to permit ease of rotation about a fixed object, for
example, without requiring that complicated control maneuvers be
performed by an operator (or, in some cases, no control maneuvers
are required to be performed at all).
[0009] In view of the above-enumerated drawbacks, it is apparent
that there exists a need in the art for systems and/or methods
which solve and/or ameliorate at least one of the above problems of
prior art vehicle control systems. It is a purpose of this
invention to fulfill these needs in the art as well as other needs
which will become more apparent to the skilled artisan once given
the following disclosure.
SUMMARY OF INVENTION
[0010] Generally speaking, this invention fulfills the above
described needs in the art by providing:
[0011] a method of controlling the directional motion of a vehicle
in response to at least one selected or detected variable, the
method comprising:
[0012] variably locating a steer center, corresponding to a steer
axis, of a vehicle in response to the at least one selected or
detected variable.
[0013] In further embodiments, this invention provides:
[0014] a system for controlling the directional motion of a vehicle
in response to at least one selected or detected variable, the
system comprising:
[0015] a control mechanism embodying a set of control instructions,
the control instructions being formulated to perform the functions
of:
[0016] variably locating a steer center, corresponding to a steer
axis, of a vehicle in response to the at least one selected or
detected variable.
[0017] Preferred embodiments of the subject invention relate
generally to the field of vehicle computer or microprocessor
control systems for omni-directional and skid steered (or
directionally steered) vehicles (including algorithms associated
therewith). In certain embodiments, this invention relates to a
control methodologies designed to be used for walk-behind,
relatively stationary, or ride-on machinery such as fork lifts,
cranes, pallet trucks, long load transporters, aircraft handling or
aircraft engine handling devices, aerial work platforms, and other
industrial machinery, as well as medical equipment including
wheelchairs, scooters, patient lifts, beds, stretchers, transport
dollies or other powered ambulatory equipment and personal mobility
devices.
[0018] In various preferred embodiments, the subject invention
provides a methodology to interrelate various variables defining
the wheel motion definitions required for a vehicle to perform a
prescribed combination of translational and rotational motions. For
example, various algorithms can be used to obtain a plurality of
different desired results (exemplary mathematical representations
of such interrelationships of the variables are provided in the
description below).
[0019] Example functionalities to which certain particularly
efficacious methods of the subject invention apply are as
follows:
[0020] a) Steer Center Determination, which is a method for causing
a vehicle to rotate around a vertical steer axis other than that
located at the geometric center of the wheel pattern. Previous
control algorithms have had the center of rotation fixed at the
center of wheel arrangement. This method permits the center of
rotation to be defined anywhere in the plane of the vehicle's
motion. An example provided herein below demonstrates the center of
rotation being defined anywhere on the longitudinal centerline of
the vehicle between the front axle center and the geometric center
of the tread rectangle. The steering axis is the point around which
the vehicle rotates.
[0021] b) Variable Steer Center, which is a method for actively
moving the steer axis of a vehicle as a function of rotational
speed, translational speed, preprogrammed definition, or other
external input. In this example, the steering axis can be actively
moved as a function of dependant variables having any specified (or
unspecified) range. The example provided herein varies the scaling
of the distance from the center of the front axle, to the center of
rotation, between the maximum value of half the length of the wheel
base, to the minimum value of zero. The scaling is a function of
the Y input command (fwd/rev) such that when Y is zero, the turn
center distance is a specified amount (B), and when Y is maximum,
the turn center distance is maximum (WB/2). This has the effect of
reducing "tail swing" as speed increases. In particular, this
example exhibits the added benefit of increased dynamic vehicle
stability.
[0022] c) Rotational Speed Limit, which is a method to limit
rotational speed as a function of translational speed,
preprogrammed definition, or other external input. In this example,
the rotational speed can be limited as a function of dependant
variables having any specified (or unspecified) range. The example
provided herein varies a parameter that limits the rotational (Z
axis) maximum motor speed command to a fraction of an external
setting.
[0023] d) Dependent Speed Limiting, which is a method to limit a
translational speed as a function of rotational speed, another
translational speed, preprogrammed definition, or other external
input. In this example, the limiting of the translational speed can
be a function of dependent variables having any specified (or
unspecified) range. In the example provided herein, speed in the X
direction (sideways) is limited as a function of the speed in the Y
direction (fwd/rev) such that X would be at maximum when Y is zero
and would reduce linearly to a fixed specified value when Y is at
maximum. Similarly, in this example, rotation speed would be
limited from a maximum to a fixed value as a function of an
increase in the translation command vector (vector summation of X
and Y). This type of speed limiting and can be referred to as
"Speed Sensitive Steering". Specifically, this function is a safety
feature that, when operating, requires more input to get a certain
yaw rate at high speed (relative to lower speeds), and provides an
ergonomic benefit, for example, by achieving a large yaw rate from
a small input at slower maneuvering speeds.
[0024] e) Dynamic Scaling, which is a method to actively rescale
input signals as a function of dependant relationships, in order to
maximize input device resolution.
[0025] It is one object of the subject invention to employ dynamic
scaling to tailor the amount of power provided to sideways
directional movement as a function of forward or reverse
directional movement (or vice versa). For example, when traveling
at high forward speeds, sideways speed is limited according to a
formula such as provided herein.
[0026] It is a further object of one embodiment of the subject
invention to provide a manually operated joystick. In such an
embodiment, for example, the sensitivity of the joystick can
optionally be reprogrammed following scanning cycles for input
variables e.g. every 20-40 milliseconds. In effect, using such an
embodiment, the range of motion of the joystick, as it corresponds
to output power, is variable continuously based on the input
variables (e.g. speed or load conditions) i.e. to improve or
optimize joystick resolution for one or more input variables.
[0027] It is yet a further object of the subject invention to
provide a system in which a single command can be employed to
perform desired vehicle directional functions e.g. to cause the
rotation of a vehicle about an object with a single control
input.
[0028] The invention will now be described with respect to certain
embodiments thereof as illustrated in the following drawings
wherein:
BRIEF DESCRIPTION OF THE DRAWINGS
[0029] FIG. 1 illustrates a plan view of a wheeled vehicle having a
steer center located at the geometric center of an omni-directional
vehicle in accordance with known vehicle control systems.
[0030] FIG. 2 illustrates a plan view of one embodiment of a steer
axis location control system according to the subject invention,
with the steer center being shown located forward of the geometric
center of the vehicle.
[0031] FIG. 3 illustrates a plan view of an alternative embodiment
of the subject invention in which the steer center of a vehicle is
variably located (moved) in response to or as a function of input
or detected variables such as vehicle speed.
[0032] FIG. 4 illustrates, in graphical form, one embodiment of a
speed vs. steer center location relationship determination such as
performed in the embodiment of FIG. 3.
[0033] FIG. 5 is an alternative embodiment of the subject
invention, illustrated in graphical form, in which a speed vs.
steer relationship is calculated to improve, maximize, and/or
optimize dynamic stability of a vehicle during vehicle
locomotion.
[0034] FIG. 6 illustrates an embodiment of the steer center control
system according to the subject invention in which the steer center
is assigned within an object within the plane of directional motion
of the vehicle.
[0035] FIG. 7 illustrates an embodiment of the steer center control
system according to the subject invention in which the steer center
is assigned at the location of the vehicle operator as determined
by the sensing of the location of a sensor located proximal or on
the vehicle operator.
DETAILED DESCRIPTION OF CERTAIN EMBODIMENTS
[0036] For a more complete understanding of the present invention
and advantages thereof, reference is now made to the following
description of various illustrative and non-limiting embodiments
thereof, taken in conjunction with the accompanying drawings in
which like reference numbers indicate like features.
[0037] Turning now initially to FIG. 1, therein is illustrated, in
plan form, a prior art vehicle control system 100 in which the
steer center of a vehicle is located at the geometric center of the
vehicle. More specifically, as can be seen in this figure, the
geometric center of the vehicle is located at point Z, along the
longitudinal centerline of the vehicle at a distance of one half of
the wheel base from the centerline of the front axle. For the
purposes of the mathematics of the example provided herein,
rotation about the steer axis at point Z is considered positive
when clockwise. The Y+direction indicated in FIG. 1 is considered
the forward direction, and the X+direction is to the right.
[0038] As aforesaid in the BACKGROUND section above, such a prior
art control system suffers from various drawbacks, some of which
are related to lack of dynamic stability, which, in turn, limits
the top speed of the vehicle.
[0039] Referring now, then, to FIG. 2, therein is illustrated, in
plan view, one embodiment of a steer axis location control system 1
according to the subject invention, with the steer center Z being
shown located forward of the geometric center C of the vehicle. In
such an embodiment, wheel motion (e.g. speed and direction)
requirements can be calculated through transformation equations for
any location of Z on the x-y plane. In this regard, the example in
FIG. 2 shows Z at a location along the longitudinal centerline of
the vehicle, an arbitrary distance B from the centerline of the
front axle.
[0040] FIG. 3, in comparison to the first two figures, depicts an
example of a variable steer center embodiment of the steer axis
location control system 1 wherein steer center Z is not fixed at
location B, but, rather, is permitted to move around in the x-y
plane as a function of other variables. Moreover, in the example,
steer center Z(y) is moved as a function of speed Y (e.g.
forward/reverse) along the longitudinal centerline of the vehicle
between an arbitrary point Z at a distance B from the center of the
front axle to a point Z' at distance B' (=WB/2) from the center of
the front axle.
[0041] Turning now to FIG. 4, this figure depicts an embodiment, in
graphical form, of steer axis location control system 1 wherein the
speed vs. steer center location relationship determination (e.g.
such as described with respect to FIG. 3). In such an embodiment,
any logical or appropriate mathematical definition and/or any
polynomial order can be used calculated from or as a function of
any number of inputs (e.g. detected variables). Furthermore, as can
be seen, the graph of the subject embodiment defines the location
of steer center Z as a linear (first order) function of the
translational speed in a forward/reverse direction. In the example
embodiment, when the Y Speed is zero, steer center Z is at distance
B from the center of the front axle. As speed Y increases, steer
center Z moves closer to the geometric center of the vehicle. When
speed Y is at its maximum, the steer center reaches distance
B'.
[0042] In certain further embodiments, such as illustrated in FIG.
5, steer axis location control system 1 determines and/or manages
the location of steering center Z by a method and/or system in
which dependant speed limiting of translation in the X (e.g.
sideways) direction is a function of speed in the Y direction (e.g.
forward/reverse). In such an embodiment, any logical or appropriate
mathematical definition and/or any polynomial order can be used
calculated from or as a function of any number of inputs (e.g.
detected variables). Moreover, in such an embodiment, sideways
speed is determined/calculated as a linear (first order) function
of forward/reverse translational speed. When speed Y is zero, the
maximum sideways speed S2 is permitted. As speed Y increases,
allowable speed X is reduced. When speed Y is at its maximum,
allowable speed X reaches value Kx. Additionally, in the example,
the limitation of speed Z (rotational speed) is an analogous
function of speed Y where the lower limit is defined as Kz.
[0043] In still further embodiments, such as illustrated in FIG. 6,
steer center Z of vehicle 3 is assigned to an object 0 located
outside the parameters of vehicle 3 (by control mechanism CM) but
within plane of motion P which, in preferred embodiments, extends
outwardly from the wheel contacting surface of vehicle 3
indefinitely. In such an embodiment, it is conceivable to locate or
assign steer center Z anywhere in plane of motion P regardless of
the distance of steer center Z from geometric center C of vehicle 3
(i.e. the location of steer center Z is not limited to within the
"four corners" of the wheels). As illustrated by the rotation
arrows A in the figure, after assigning the location of steer
center Z, vehicle 3 can be rotated about object 0 automatically
such as by manually inputting a single input signal or
automatically, as desired.
[0044] In yet another embodiment, as shown in FIG. 7, in a walk
behind version of vehicle 3 employing a control handle 5, as
illustrated, control mechanism CM can automatically, or by manual
operation, assign steer center Z at a location corresponding to the
location of a human vehicle operator 7. In a preferred embodiment
of FIG. 7, the location of operator 7 is constantly or periodically
monitored and/or detected using a sensor S located on or proximal
the operator. Afterwards, vehicle 3 can be rotated about operator 7
automatically, again, such as by manually inputting a single input
signal or automatically, as desired. In such an embodiment, by
assigning the location of the steer center of the vehicle as such,
walk behind-type vehicles can be rotated without requiring that
vehicle operator "run around" the vehicle as would be required if
the vehicle were rotated about its geometric center C.
[0045] In further preferred embodiments, when a load carrying
vehicle is being operated, the center of gravity of such a load
carrying vehicle can be automatically or manually recalculated so
that steer center Z can be located as a function of the position
thereof. In such embodiments, locating steer center Z as such
allows vehicle 3 to be operated in a manner which is dynamically
stabilized (e.g. preferably optimally). For example, in one such
embodiment, steer center Z would be continually monitored and/or
repositioned as the center of gravity of vehicle 3 is caused to
change (e.g. during monitoring cycles).
[0046] Example Equations Demonstrating Each Method:
[0047] Definitions of variables used in examples and in the
drawings:
[0048] 1) Wheelbase--WB
[0049] 2) Tread Width--T
[0050] 3) Turn Center Distance--B
[0051] 4) Rotation Speed Reduction Factor--R (%)
[0052] 5) X Intercept speed--Kx, the max. allowable X direction
speed at max. Y speed
[0053] 6) Z Intercept Speed--Kz, the max. allowable rotational
speed at max. Y speed
[0054] 7) Maximum Vehicle Speed--S, Y direction speed (Fwd/Rev)
[0055] 8) Proportional Input Values--P(X,Y,Z)(1,2,3,4) range
definitions (0-255)
[0056] 9) Discrete Input Value--P Limit on maximum speed in
percent.
[0057] The sequence of method logic for this example is:
[0058] 1) Determine number of significant units on each of six
input axes, between neutral zone, and max. valid value, and a
direction indicator.
[0059] 2) Calculate the Speed Limits for translation and rotation
by applying predetermined or input restrictions.
[0060] 3) Calculate the Relative Limits for each of six axes by
modifying the Speed Limits by applying the joystick position slope
intercept relationship equations.
[0061] 4) Compute six scaling factors by proportioning the relative
limits over the available range of scaling units.
[0062] 5) Compute six values of wheel speed by multiplying scaling
factor by the corresponding joystick command.
[0063] 6) Determine the steer center location based on the Y
input.
[0064] 7) Calculate the steer correction factor for the current
steer center location.
[0065] 8) Solve the superposition matrix to obtain four speed and
direction commands, one for each wheel.
[0066] 9) Send speed and direction commands to the drive.
[0067] The equations required for each of the steps above are as
follows:
[0068] 1) Speed Limits: S2=S.times.P S3=S2.times.R
[0069] 2) Relative Limits: In the slope intercept form
Y=m.times.X+b
[0070]
Sx+=(-1.times.(S2-Kx)/(PY4-PY3).times..vertline.Y.vertline.)+S2
[0071] Sx-=(-1.times.(S2-Kx)
(PY2-PY1).times..vertline.Y.vertline.)+S2
[0072] Sy+=S2
[0073] Sy-=S2
[0074]
Sz+=((-1.times.(S3-Kz)/((PY4-PY3).times.1.4142)).times.((X.sup.2+Y.-
sup.2).sup.0.5))+S3
[0075]
Sz-=((-1.times.(S3-Kz)/((PY2-PY1).times.1.4142)).times.((X.sup.2+Y.-
sup.2).sup.0.5))+S3
[0076] 3) Scaling factors:
[0077] +Xscale=Sx+/(PX4-PX3)
[0078] -Xscale=Sx-/(PX2-PX1)
[0079] +Yscale=Sy+/(PY4-PY3)
[0080] -Yscale=Sy-/(PY2-PY1)
[0081] +Zscale=Sz+/(PZ4-PZ3)
[0082] -Zscale=Sz-/(PZ2-PZ1)
[0083] 4) Wheel Speed Values:
[0084] +Xspeed=.vertline.X.vertline.x+Xscale
[0085] -Xspeed=.vertline.X.vertline..times.-Xscale
[0086] +Yspeed=.vertline.Y.vertline.x+Yscale
[0087] -Yspeed=.vertline.Y.vertline..times.-Yscale
[0088] +Zspeed=.vertline.Z.vertline.x+Zscale
[0089] -Zspeed=.vertline.Z.vertline..times.-Zscale
[0090] 5) Steer Center Determination:
[0091]
B2=(((WB/2)-B)/(PY4-PY3)).times.((X.sup.2+Y.sup.2).sup.0.5)+B
[0092] 6) Steer Center Corrections:
[0093]
FAM=(((T/2).sup.2+B2.sup.2).sup.0.5)/(((T/2).sup.2+(WB/2).sup.2).su-
p.0.5)
[0094]
RAM=(((T/2).sup.2+(WB-B2).sup.2).sup.0.5)/(((T/2).sup.2+(WB/2)
2).sup.0.5)
[0095] 7) Apportioned Wheel Speed Values:
[0096] LF=Xspeed+Yspeed+(Zspeed'FAM)
[0097] RF=Xspeed+Yspeed+(Zspeed'FAM)
[0098] LR=Xspeed+Yspeed+(Zspeed.times.RAM)
[0099] RR=Xspeed+Yspeed+(Zspeed.times.RAM)
[0100] Note that the variables in the above equations are not
signed, nor are axis specific speeds designated. These should be
determined through proper logic within the program and must include
corrections to signs (i.e. +/-) for motor reversal required by
vehicle structure.
[0101] Once given the above disclosure, many other features,
modifications, and improvements will become apparent to the skilled
artisan. Such other features, modifications, and improvements are
therefore considered to be part of this invention, the scope of
which is to be determined by the following claims:
* * * * *